The invention relates to a method for coding traffic hindrances that encroach upon the street, in digitally coded traffic messages which contain as elements a location situated on a street and the extent and direction of the traffic hindrance, and which are decoded on the basis of a location table or a digital map.
A design of this type and a coding of this type of traffic message is established, by way of example, in the CEN EN 12313-1, which is based on the draft code ALERT C, November 1990, published by the RDS ATT ALERT Consortium. Thus using the radio-data system (RDS), an additional and inaudible transmission of digital data is possible in a data channel parallel to radio programs. In this context, the essential elements of a traffic message are the location of the event and the event. This data is cataloged, which means that each traffic-relevant location and each traffic-relevant event is assigned a unique code. Linking the locations in a location table along existing streets describes the pattern. In order to exploit the traffic message channel (TMC), in addition to the customary devices of a receiving apparatus having an RDS decoder, devices for decoding, storing, processing, and outputting the traffic messages are necessary.
Digitally coded traffic messagesxe2x80x94hereinafter also termed TMC messages, for the sake of simplicityxe2x80x94can be transmitted not only using the radio-data system, but also, for example, within the digital audio broadcast (DAB), especially in an FI channel (Fast Information Channel). In addition, transmission of messages over mobile telephony networks is provided, the broadcast channel and the SMS channel (Short Message Service) being suitable for this purpose. Currently, in this regard, a Global Automotive Telematic Standard (GATS) is being worked out. This is a packet-oriented data channel, which can be processed parallel to a voice telephone call. Whereas, in the radio systems, i.e., in uni-directional networks, all TMC messages are transmitted one after the other, in bidirectional networks transmission is possible upon request.
In a TMC message, only one location code is transmitted in each case. In order to be able to calculate the end point of a traffic hindrance, the direction and the extent of the traffic hindrance are also transmitted. The extent indicates how many segments of a street are affected by the traffic hindrance. The direction indicates in which direction the end point of the traffic hindrance lies. In this context, all locations affected must be on the same street.
References to other streets only come about as a result of the fact that a linkage of the streets (Intersection Code) is generated at the level of the location, reference being made in the intersection code to the location of the intersecting streets, which are also coded in the location table. This intersection code heretofore has only aided in realizing navigational applications within the location table and in checking the plausibility of the location table itself. If the traffic hindrances affect more than one street, they can only be coded in the known method by generating a plurality of messagesxe2x80x94one for each of the streets in question.
The objective of the present invention is to code traffic hindrances based on the location table so that traffic hindrances that extend over more than one street can also be decoded and reproduced in a form that is easy to absorb by the user.
This objective is achieved in the method according to the present invention as a result of the fact that in the case of reported traffic hindrances, which, due to their size, extend beyond a junction and onto a different street, a further element is used to code the information, on which of the bifurcating streets, in which direction, and how far, the reported traffic hindrance extends.
The present invention can be applied to junctions and intersections, the term junction being used throughout to describe the present invention, because an intersection can also be considered as a multiple junction.
In the TMC system that is standard throughout Europe, the method according to the present invention can be applied through the fact that the digital coding of the traffic messages takes place in accordance with the ALERT-C protocol, and that the additional element is label 12.
As a result of the present invention, a higher percentage of existing traffic messages is accessible to direct coding. In contrast to splitting up the information in a plurality of messages, the messages that are generated in this manner are easier to register, they generally reduce the channel capacity required, and they therefore increase the attractiveness of the RDS-TMC system for operators and users.
The method according to the present invention is compatible with existing data terminals in the sense that no false information is generated. Receivers that cannot interpret label 12 receive a reduced scope of information on the cause of the disturbance and receive a partial range of the routes affected by the disturbance.
It is especially advantageous to apply the method according to the present invention in expanding the RDS-TMC system to urban areas where traffic hindrances encroaching upon the street are a regular occurrence, as a result of which the currently used protocol operates at its limits.
One advantageous embodiment of the method according to the present invention lies in the fact that the data field of label 12 contains three bits for the selection of the street connecting to the junction on which the traffic hindrance is located, one bit for the relevant direction, four bits for the extent of the hindrance on this street, and in the fact that eight further bits for identical coding are provided in the event that the traffic hindrance also extends beyond a further street change. In this context, it can be preferentially provided that when the traffic hindrance extends over more than three streets, a supplemental label 12 is coded and transmitted for each of the two further streets. In this embodiment, the 16-bit data field contained in label 12 is exploited in a particularly beneficial manner
The present invention also relates to a method for decoding traffic messages that were coded using the method according to the present invention. In this method, in which a traffic message is provided with a location, a street, a direction, and an extent and that concerns a traffic hindrance, label 12 is interpreted such that, proceeding from the intersection of the streets coded in the traffic message, on the basis of the street coded in label 12 and in the direction indicated in label 12, and as a result of the extent indicated in label 12, the location is determined which, in the event that no further extension of the traffic hindrance is coded in label 12, indicates the end of the traffic hindrance. If the end of the traffic hindrance is not located on this street, then, in this context, it is possible to proceed such that in coding a further street in label 12, the location of the end of the traffic hindrance is read out from the location table along the further street.